> ## Documentation Index
> Fetch the complete documentation index at: https://docs.lithtrix.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Delegate with signing

> Client-side Ed25519 signing for delegation contracts

# Delegate

**MCP:** `lithtrix_delegate` (signs locally — do not pass `signature` manually)\
**REST:** `POST /v1/agents/{parent_agent_id}/delegate`\
**Auth:** Root `ltx_*` + active passport on parent.

## Contract shape

Request field name is **`contract`** (not `contract_json`).

```json theme={null}
{
  "read_set": ["memory"],
  "write_set": ["memory"],
  "assumptions": {},
  "version_refs": [],
  "ttl_seconds": 3600,
  "verifier_obligations": null,
  "conflict_policy": "last_writer_wins_audit"
}
```

`conflict_policy` must be exactly **`last_writer_wins_audit`** (underscores, not hyphens).

## Signing (`sign_payload`)

UTF-8 bytes to sign:

```
lithtrix.delegation.contract.v1\n
<recipient_agent_id_uuid>\n
<task_id_uuid>\n
<contract_json_minified_sorted_keys_utf8>
```

Sign with your passport Ed25519 private key → RFC4648 base64 raw signature.

**MCP:** set `LITHTRIX_PASSPORT_MASTER_SEED` or `LITHTRIX_PASSPORT_PRIVATE_KEY`.\
**Operator-derived keys:** see [Passports — operator-derived keys](/passports#operator-derived-keys).

## Signing test vector

Verify your implementation locally before hitting the live API. **TEST ONLY — do not use this private key in production.**

| Field                              | Value                                                                                                                                                                         |
| ---------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `recipient_agent_id`               | `aaaaaaaa-bbbb-cccc-dddd-eeeeeeeeeeee`                                                                                                                                        |
| `task_id`                          | `11111111-2222-3333-4444-555555555555`                                                                                                                                        |
| `contract` (minified, sorted keys) | `{"assumptions":{},"conflict_policy":"last_writer_wins_audit","read_set":["memory"],"ttl_seconds":3600,"verifier_obligations":null,"version_refs":[],"write_set":["memory"]}` |
| Ed25519 private seed (hex)         | `0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef`                                                                                                            |
| Expected signature (base64)        | `LIxXYXgfJqTGRblhdHQovWaVxdGPeVHzYNakLtpE9MCeGlFzXraL9Bbjwf9FDX/ehjXH9znNnhTyexqepSJ8Aw==`                                                                                    |

Canonical UTF-8 string to sign (exact bytes):

```
lithtrix.delegation.contract.v1
aaaaaaaa-bbbb-cccc-dddd-eeeeeeeeeeee
11111111-2222-3333-4444-555555555555
{"assumptions":{},"conflict_policy":"last_writer_wins_audit","read_set":["memory"],"ttl_seconds":3600,"verifier_obligations":null,"version_refs":[],"write_set":["memory"]}
```

`POST /v1/auth/passport/verify` is the challenge→session passport flow — **not** a delegation signing debug endpoint.

## Response

Returns `delegation_id`, `task_id`, and (MCP only) `_lithtrix.next_tool: lithtrix_trace_append`.